Astronomers have used an X-ray image to make the first detailed study of
the behavior of high-energy particles around a fast moving pulsar. The
image, from NASA's Chandra X-ray Observatory, shows the shock wave
created as a pulsar plows supersonically through interstellar space.
These results will provide insight into theories for the production of
powerful winds of matter and antimatter by pulsars.

Chandra's image of the glowing cloud, known as the Mouse, shows a stubby
bright column of high-energy particles, about four light years in
length, swept back by the pulsar's interaction with interstellar gas.
The intense source at the head of the X-ray column is the pulsar,
estimated to be moving through space at about 1.3 million miles per
hour.

A cone-shaped cloud of radio-wave-emitting particles envelopes the X-ray
column. The Mouse, a.k.a. G359.23-0.82, was discovered in 1987 by radio
astronomers using the National Science Foundation's Very Large Array
in New Mexico. It gets its name from its appearance in radio images that
show a compact snout, a bulbous body, and a remarkable long, narrow,
tail that extends for about 55 light years.

"A few dozen pulsar wind nebulae are known, including the spectacular
Crab Nebula, but none have the Mouse's combination of relatively young
age and incredibly rapid motion through interstellar space," said Bryan Gaensler of the Harvard-Smithsonian Center for Astrophysics
and lead author of a paper on the Mouse that will appear in an upcoming issue
of The Astrophysical Journal. "We effectively are seeing
a supersonic cosmic wind tunnel, in which we can study the effects of a
pulsar's motion on its pulsar wind nebula, and test current theories."

Pulsars are known to be rapidly spinning, highly magnetized neutron
stars -- objects so dense that a mass equal to that of the Sun is packed
into a diameter of about 12 miles. Their formation is associated with a
Type II supernova, the collapse and subsequent explosion of a massive
star. The origin of a pulsar's high velocity is not known, but many
astrophysicists suspect that it is directly related to the explosive
circumstances involved in the birth of the pulsar.

The rapid rotation and strong magnetic field of a pulsar can generate a
wind of high-energy matter and antimatter particles that rush out at
near the speed of light. These pulsar winds create large, magnetized
bubbles of high-energy particles called pulsar wind nebulae. The X-ray
and radio data on the Mouse have enabled Gaensler and his colleagues to
constrain the properties of the ambient gas, to estimate the velocity of
the pulsar, and to analyze the structure of the various shock waves
created by the pulsar, the flow of particles away from the pulsar, and
the magnetic field in the nebula.

Other members of the research team were Eric van der Swaluw (FOM
Institute of Physics, The Netherlands), Fernando Camilo (Columbia Univ.,
New York), Vicky Kaspi (McGill Univ., Montreal), Frederick K. Baganoff
(MIT, Cambridge, Mass.), Farhad Yusef-Zadeh (Northwestern), and Richard
Manchester (Australia Telescope National Facility). The pulsar in the
Mouse was originally detected by Camilo et al. in 2002 using Australia's
Parkes radio telescope. Chandra observed the Mouse on October 23 and
24, 2002.